The Area Under a Graph of V_x Vs $\frac { 1 } { 2 }$

Multiple Choice

The area under a graph of v_x vs.t from t = t_i to t = t_f represents

A) x_i.
B) x_f.
C) x_f- x_i.
D) $\frac { 1 } { 2 }$ (x_i + x_f) .
E) x_i + x_f.